The invention relates to storage and retrieval machines, and more particularly to carriage side guide roller arrangements for storage and retrieval machines.
A conventional storage and retrieval machine includes a base movable horizontally along the floor. A mast extends upwardly from the base, and the upper end of the mast runs along a rail supported above the floor. A carriage moves vertically along the mast, and a shuttle moves horizontally relative to the carriage for depositing loads on and picking up loads from a storage rack adjacent the storage and retrieval machine.
The carriage is typically supported for movement along the mast by a plurality of rollers engaging generally vertical surfaces on the mast. Among these rollers are the carriage side guide rollers, which engage mast surfaces extending perpendicular to the direction of carriage and base movement. During the normal vertical cycle of the carriage the carriage side guide rollers are under very little load. However, high forces are realized in the carriage side guide rollers when the shuttle extends to pick up or deposit loads. These forces increase significantly with long reach shuttle cycles and/or with heavier loads.
The high forces on the carriage side guide rollers cause high roller contact pressure on the mast. This can cause excessive wear and deflection in the parent metal, ultimately resulting in mast and/or roller failure. Rollers have been made larger or duplexed in order to handle these high loads. This results in cost increases and mounting problems.